Resolved Magnetospheric Imaging of an Extrasolar Jovian Radiation Belt Analog

Planets host some of the most energetic plasma structures in the Solar System: radiation belts of relativistic particles up to tens of megaelectron volts in energy that can extend further than ten times the planet’s radius, emit gradually varying radio emissions, and affect the surface chemistry of close-in moons. In this era of comparative magnetospheric science, radio observations in the last decade demonstrated that brown dwarfs and very low mass stars, collectively known as ultracool dwarfs, can serve as magnetic analogs to gas giant planets. In addition to aurorae, ultracool dwarfs also exhibit a non-auroral radio component long hypothesized to trace stellar coronal activity or extrasolar radiation belt analogs. We present high resolution imaging of the ultracool dwarf LSR J1835+3259 at 8.4 GHz demonstrating that its quiescent radio emission is analogous to Jupiter’s synchrotron radiation belts and discuss implications for exoplanet dynamo theory, searches for brown dwarf satellites, and the possibility of extrasolar volcanism.